长江流域主要干/支流水化学特征及外源酸的影响

为了探究人类活动对长江流域水化学特征的影响,本文以流域内主要干/支流代表断面的采样点为研究对象,分别于2016年丰水期和平水期采集地表水样各13组,通过离子比值法、主成分分析法和化学离子平衡计算法,综合分析水化学特征,并估算碳酸和外源酸参与碳酸盐岩的溶蚀比例.结果表明,水化学类型主要为HCO₃-Ca型,指示流域内水化学的主要影响因素为碳酸盐岩的溶解,在碳酸盐岩风化过程中,碳酸与碳酸盐岩的相对快速风化为主导反应.此外,丰水期和平水期各采样点碳酸溶蚀比例均值分别为60.33%和59.14%,不同采样点的溶蚀比例差值较大,指示外源酸对河流与岩石侵蚀风化过程的影响不容忽视,且阳离子交换对水化学有一定影响,但并不是主要的反应过程.与多年前水文监测初期的数据相比,硫酸和硝酸对岩石风化作用加强,人为因素对长江的水质影响增大.     

A novel sigma coordinate system to simulate abrupt changes of underwater terrain in a hydrodynamic model: application to Lake Mead,USA

The sigma (SIG) coordinate system in ocean circulation simulation models results inevitably in horizontal pressure gradient error. This problem also emerges in models of deep lakes or reservoirs with the same characteristics of underwater terrain mutation. SIG coordinates reflect vertical relative stratification but cannot be used to calculate horizontal pressure gradient force in places with drastic topographic changes; this results in vertical water temperature and circulation errors. In deep lakes or reservoirs, differences in water density caused by the temperature difference between upper and lower water bodies is the primary cause of thermal stratification phenomena. Lake Mead was used as a case study on steep topography based on Environmental Fluid Dynamics Code (EFDC) model in this study. SIG coordinates result in close agreement between the calibrated temperature time series at the top and middle water layers, but disparity in the bottom water layer. The error emerges in the horizontal pressure gradient error due to the SIG coordinate transformation. Neither increasing the vertical resolution nor adjusting the horizontal viscosity coefficient resolve this error. We test the sigma-zed (SGZ) coordinate which combines Z coordinate and SIG coordinate as a replacement for the SIG coordinate to find that they effectively reduce the model’s runtime and simulation efficiency. The vertical temperature distribution in SGZ coordinate mode is more accurate than the distribution in SIG coordinate mode. The Navier-Stokes horizontal gradient and advection diffusion equation results under SIG coordinates are very sensitive to the pressure gradient. The replacement also enhances resolution near the thermocline, facilitates reclosing of the water bottom and the equal sigma surface, lends significant advantages in terms of vertical temperature in the simulation for local deep water with steep terrain, and shortens runtime for 0.14 h. SGZ mixed coordinates are recommended in the simulation of deep lakes or reservoirs wherein the underwater topography is large (with abundant continuous deep trenches or reefs).

     

Effects of rainfall on surface environment and morphological characteristics in the Loess Plateau

Environmental Science and Pollution Research - Slope failure is a one of major process that causes severe landform variation and environment variation, and slope failure has become a major hidden...     

A comparative study on the raw chitin and chitosan yields of common bio-waste from Philippine seafood

Environmental Science and Pollution Research - Bio-waste materials from aquatic species are alternative sources of chitin and chitosan—high-value natural biodegradable and biocompatible...     

Heterogeneous Fenton degradation of ofloxacin catalyzed by magnetic nanostructured MnFe2O4 with different morphologies

Environmental Science and Pollution Research - Magnetic nanostructured MnFe2O4 with different morphologies, synthesized via chemical co-precipitation and hydrothermal method, was assayed as...     

Applicability of hybrid bionic optimization models with kernel-based extreme learning machine algorithm for predicting daily reference evapotranspiration: a case study in arid and semiarid regions,China

Environmental Science and Pollution Research - The accurate prediction of daily reference crop evapotranspiration (ETO) enables effective management decision-making for agricultural water...     

Application of improved seasonal GM(1,1) model based on HP filter for runoff prediction in Xiangjiang River

Environmental Science and Pollution Research - Runoff forecasting is essential for the reasonable use of regional water resources, flood prevention, and mitigation, as well as the development of...     

Comprehensive assessment of toxic metals in urban and suburban street deposited sediments (SDSs) in the biggest metropolitan area of China

A set of toxic metals, i.e. As, Hg, Pb, Cd, Cu, Zn, Ni and Cr, in urban and suburban SDSs were investigated comparatively in the biggest metropolitan area of China, Shanghai. Results showed that all of the metals except As were accumulated greatly, much higher than background values. Geo-accumulation index indicated that metal contamination in urban SDSs was generally heavier than that in suburban SDSs. Potential ecological risk index demonstrated that overall risks caused by metals were considerable. Cd contributed 52% to the overall risk. Multivariate statistical analysis revealed that in urban SDSs, Zn, Ni, Cd, Pb, Cu and Cr were related to traffic and industry; coal combustion led to elevated levels of Hg; soil parent materials controlled As contents. In suburban SDSs, Pb, Cu, As and Cd largely originated from traffic pollution; Zn, Ni and Cr were associated with industrial contaminants; Hg was mainly from domestic solid waste.     

Ambient TSP concentration and dustfall in major cities of China: Spatial distribution and temporal variability

Based on environmental monitoring data in 93 major cities and meteorological records at 398 weather stations in China from 1981 to 2007, total suspended particle (TSP) concentration, the intensity of dustfall, and sand and dust storm frequency (F_d) were analysed. During the past 27 years, the annual average TSP concentration (C_TSP) in 93 cities was 402 μg m^?3. Annual average C_TSP decreased from the north to the south and from inland to the coast areas with a peak value of 628.8 μg m^?3 in Lanzhou. In the 1980s, 1990s and 2000s, annual average C_TSP was 628.7, 319.2, and 250.1 μg m^?3, respectively. Annual average intensity of dustfall (I_d) was 240.5 t km^?2 a^?1, decreased from northern to southern China and from inland to the coast areas with the maximum value of 717.2 t km^?2 a^?1 in Baotou. In the 1980s, 1990s and 2000s, annual average I_d was 334.8, 220.9, 146 t km^?2 a^?1 respectively. Annual average I_d in the Loess Plateau region was commonly higher than 200 t km^?2 a^?1. The annual average F_d decreased from arid regions in northwestern China to humid areas in southeastern China with two sand and sand storm centers existing in Xinjiang Taklamakan Desert and western Inner Mongolia. The annual average F_d in the 1980s, 1990s, 2000s was 16, 8, 6 days respectively, decreased steadily from 18 days in 1981–5 days in 2007. Annual average I_d had a positive linear relation to annual average C_TSP (R² = 0.96). Annual average F_d had a positive relation with annual average C_TSP (R² = 0.97) as well as annual average I_d (R² = 0.94). TSP was the chief pollutant influencing Air Pollution Index (API) in northern China in spring and winter seasons. Sand and dust storm might be a major factor affecting the temporal variability and spatial distribution of TSP and dustfall in China.     

Potentially toxic metal contamination of urban soils and roadside dust in Shanghai, China

A detailed investigation was conducted to understand the contamination characteristics of a selected set of potentially toxic metals in Shanghai. The amount of Pb, Zn, Cu, Cr, Cd and Ni were determined from 273 soil/dust samples collected within urban area. The results indicated that concentration of all metals except Ni in soils was significant, and metal pollution was even severer in roadside dust. A series of metal spatial distribution maps were created through geostatistical analysis, and the pollution hotspots tended to associate with city core area, major road junctions, and the regions close to industrial zones. In attempt of identifying the source of metals through geostatistical and multivariate statistical analyses, it was concluded as follows: Pb, Zn and Cu mainly originated from traffic contaminants; soil Ni was associated with natural concentration; Cd largely came from point-sourced industrial pollution; and Cr, Ni in dust were mainly related to atmospheric deposition.